This invention relates generally to radiation imager arrays and more specifically to automated methods and apparatus for the repairs of such arrays.
Complex electronic devices are commonly formed on substrates in fabrication processes involving deposition and patterning of multiple layers of s conductive, semiconductive, and dielectric materials to form multiple individual electronic components. For example, large area imager arrays are fabricated on a wafer. These arrays contain photodiodes and circuitry for reading the output of the photodiodes. The circuitry includes scan (address) lines, data lines and switching components (e.g., field effect transistors (FETs)). In such an array, both scan and data lines are contacted using separate sets of contacts on the panel. Additionally, half of the drive electronics are connected to a set of contacts on the outer edge of the panel which connect to xe2x80x9coddxe2x80x9d scan lines. Between these contacts and an active area of the panel are another set of contacts which connect to xe2x80x9cevenxe2x80x9d scan lines. Sense electronics are on the remaining two sides of the panel. One set of sense electronics connects to all xe2x80x9coddxe2x80x9d data lines on one side of the panel and the other set of sense electronics connects to xe2x80x9cevenxe2x80x9d data lines on the opposite side. None of the scan or data lines are contacted on both sides of the panel.
Defects in such imager arrays can result from, among other causes, impurities in materials deposited to form the various components. One example of such an impurity-based defect is a short circuit between a data line and an underlying scan (address) line in the pixel array. Such short circuits disrupt the desired electrical connections between devices in the array and seriously degrade performance of one or more individual electronic components on the wafer, often to the point of making an entire wafer unusable. In order to improve the yield of flat panel X-Ray detectors, shorts between a scan line and a data line, which would normally result in both the data line and the scan line being unusable, are removed in a fashion that allows both the scan and the data line to be recovered with only a small number of pixels being lost in an immediate vicinity of the short. Generally two cuts are made on either side of the short on the line which can be most easily recovered (or xe2x80x9crepairedxe2x80x9d).
Repair and recovery of data lines that have been cut on flat panel x-ray panels are made possible by addition of a small number of uncommitted contacts.
Uncommitted contacts are connected to a xe2x80x9cfreexe2x80x9d end of a data line that has been cut in two places to remove a short. A free end of a data line in this instance refers to a cut end of a data line that is no longer attached to sense electronics on an opposite side because of the cut. Without recovery, data on this free end would normally be lost, representing loss of at least a partial (data) line for every short removed by cutting.
Uncommitted contacts on the opposite end can be used to short to the free end of a cut data line. In effect, a free end of an xe2x80x9coddxe2x80x9d cut data line becomes a partial xe2x80x9cevenxe2x80x9d data line by connection to an uncommitted contact on the end opposite where the xe2x80x9coddxe2x80x9d sense electronics.
The uncommitted contacts are not connected to any data lines during fabrication, but are designed to allow a short between a free end of a cut data line and an uncommitted contact to be made easily on the panel. When a data line has been cut and is connected to an uncommitted contact, data from the free end of the cut data line will be displaced spatially in the resulting acquired image. Because this image is represented as an array of binary numbers in computer memory, displaced data can be re-mapped to its correct location in the image presented for diagnosis using simple computer-based replacement algorithms. A part of this process particular to each panel is a set of locations at which cuts have been made and which uncommitted contacts have been used to recover cut data lines. It has been suggested that during the process of test and repair, a file be created to record both locations of cuts and locations of uncommitted contacts which have been used to recover cut data lines.
This file would have to accompany the panel to a system that uses this panel to generate diagnostic quality x-ray images, to enable the system to reconstruct an image from the repaired panel. This data would be different for every panel.
Successfully transferring remapping information to end users can be difficult due to logistics. Loss of data in a remapping information file can occur for various reasons, for example, corruption of data in the file itself, or loss or destruction of the media. If the file is not successfully transferred, the file must be regenerated, or else the detector assembly may become useless scrap. It would therefore be desirable to provide methods and apparatus that would make transfer of remapping information files to end users unnecessary. It would also be desirable to automate this remapping at a site of an end user.
A method is disclosed for detecting repairs made and data lines cut in an imaging array which includes an array of pixels for measuring radiation, and a plurality of data lines for reading data from the pixels, and a number of uncommitted data line contacts to be used for repairing shorted data lines. The method includes the steps of initializing the pixels of the imaging array, determining a signal level for the data lines that have not been cut, measuring a signal level of each data line in the array, and determining if the signal level for each data line is equivalent to the uncut data line signal level.
The above described method eliminates the need for shipping remapping information files with repaired detectors. In addition, the possibility that the media containing the remapping information file is compromised during shipping of the imaging array is eliminated.